1. Field of the Invention
The invention relates to a moving picture receiving apparatus which compensates image data being lost through the television signal transmission path.
2. Description of the Prior Art
FIG. 3 shows a conventional moving picture receiving apparatus, and is a block diagram of a principle construction of the image data transmission system disclosed in the Japanese patent publication No. 3-124183, the title of which is "image decoding apparatus for compensating abandoned cells". In the figure, 8 is a block disassembling portion, 9 is a block assembling portion, 10 is a coding portion, 11 is a transmission path, 12 is a decoding portion, 13 is a comparison result information transmitting means, 14 is an abandoned cell compensation means.
The operation of the above prior art is explained here. In FIG. 3, an input image signal 200 is assembled into blocks in the block assembling portion 9, and the blocked signals are processed in succeeding circuits. The blocked image data 201 are coded into a coded image signal in the coding portion 10. The blocked image data are also inputted into the comparison result information transmitting means 13. The comparison result information transmitting means 13 compares the blocked image data 201 with a block at the same position of the preceding frame, and produces a comparison result information 202 which indicates "larger" or "smaller" than the predetermined threshold value. The coded image data 203 and the comparison result information 202 are transmitted to the decoding portion 12 via the transmission path 11. The coded image data 203 are decoded into image data 204 for every block in the decoding portion 12.
The image data 204 for every block am generally converted into a linescan data, that is, output image data 205 at the block disassembling portion 8.
In case that errors occur through the transmission path 11 and are included in the coded image data 203, or the coded image data 203 can not be regenerated by data abandonment, the coded image data 203 are compensated by the comparison result information 202.
The method for compensating the coded image data 203 is explained below. When the comparison result information 202 indicates "smaller" than the threshold level, the coded image data 203 is compensated by the DC (direct current) component of the block corresponding to the block of the preceding frame. When the comparison result information 202 indicates "larger" than the threshold level, the coded image data 203 is compensated by the DC component of the blocks adjacent to the abandoned block of the same frame. This compensation can reduce influences of the image quality when the data are abandoned in the transmission path 11.
Since the conventional moving picture receiving apparatus is constructed as being described above, if the image data includes the lost or abandoned data, the DC component errors are reduced by compensating lost data using the comparison result information. Therefore, the visual degradation of the picture can be decreased.
But, it is necessary to provide an additional apparatus for transmitting the comparison result information from the transmitting apparatus to the receiver. Therefore, there occurs a problem that the transmitting efficiency decreases in the total system.
It is an object of the present invention to provide a moving picture receiving apparatus which decreases image degradation of the picture including the lost picture block which can not be reproduced, and gives less physical disorder of the picture, without providing any additional apparatus to the transmitting apparatus and without transmitting additional information from the transmission apparatus to the receiving apparatus.